Method of removing oxides, oils, and grease from an uncoated metal article



M. RIPOCHE G OXIDES, OILS AND GREASE FROM AN UNCOATED METAL ARTICLE Filed July 24, 1946 N Am zz/rz a .0 v R I A I W 7//flI///ll////I w m m 232 2% a A W w 9 l F 6 w M Patented May 6, 1952 METHOD OF REMOVING OXIDES, OILS, AND

GREASE FROM ARTICLE AN UNCOATED METAL Christian Andr Maurice Ripoche, Paris, France Application July 24, 1946, Serial No. 685,950 g I In France January 8, 1946 a 1 Claim. (01. 134-10 This invention relates to a method for the treatment of metallic pieces with a view to effecting any coating operation and more particularly to enamelling.

For scouring metallic pieces, for instance metal sheets, with a view to covering them with a coating such as an enamel layer an acid bath (sulphuric acid or hydrochloric acid) is used into which the pieces to be scoured are immersed.

This known method offers numerous drawbacks:

1. Acid baths emit acid vapors which are injurious for the workmen. In spite of the ventilations required by the regulations the workmen are not always protected against the dangerous action of said vapors.

2. The vats containing the acid baths must be H acid-resisting. Lead covered vats the main;

tenance of which is easy or sandstone vats which are very expensive and fragile must be used.

The present invention has for its object to fats covering the pieces are first burnt ofi, where-i after the formed oxides are destroyed which i makes it possible to scour the metallic pieces] Without the use of acids. According to a form of carrying out the above mentioned method the metallic pieces to be treat ed are first heated in an oxidizing atmosphere in order to burn off the fats which cover said pieces, whereafter the latter are heated in a reducing atmosphere which makes it possible to destroy the oxides formed by the heating operation or existing formerly on the pieces.

The invention also covers the hereinafter de scribed characteristic features and their various possible combinations.

Devices for carrying out the methods according to the invention are shown by way of examples in the appended drawings, in which:

Figures 1 and 2 are respectively a vertical and a horizontal sectional view of a furnace for efiecting the first operation of the method.

Figure 3 and 4 are respectively a vertical and a horizontal sectional view of a furnace for effect ing the second operation of the method.

Figure 5 is a sectional plan view showing a complete plant with two continuous furnaces.

Figure 6 is a longitudinal sectional view of said complete plant with a single movable hearth.

According to the invention the sheet metal pieces to be covered with: a coating as for example enamel are treated preliminarily in the following manner:

a. In the course of a first operation the fats which cover the sheet metal pieces are burnt off. Said fats generally come from the chasing operation and their presence would prevent the coating to adhere to the metal.

Said burning operation is effected at a temperature varying with the composition of the oil which covers the sheet metal, for example between 300 and 600 C. A stationary or continuous furnace with an oxidizing atmosphere is used.

b. A second operation consists in scouring the piece in a stationary or continuous furnace in a reducing atmosphere at temperatures varying between 700 and 850 C.

This second operation'has for its purpose to destroy:

a. The oxides which covered the metallic piece at the beginning of the treatment, and

b. The oxides which have formed on the surface of said piece in the course of the first buming operation.

The temperature of the furnace used for the second operation depends upon the nature of said oxides to be destroyed.

After said treatments the metallic pieces leave in a white condition and without any oil. The coating e. g. enamel, is applied directly onto their surface by the usual methods.

For carrying out the above described method or similar methods the devices which are shown diagrammatically in Figures 1 to 6 of the drawings can be used.

The first burning operation is effected in an ordinary furnace like that which is shown in Figures 1 and 2.

The scouring operation in a reducing atmosphere is effected in a furnace 2 with a muflle 3 (Figures 3 and 4). The pieces to be secured are introduced into the first part 3 of the muflle which plays the part of a lock and then pushed into the opposite end or rear part of said muflle.

The furnace for effecting the first operation can also be provided with a movable hearth 5 moved by the rotation of two centre bosses 6 6 and passing with a slow-.speed through a tunnel furnace I.

Said furnace (Figure 5) is located near a similar furnace making it possible to effect the second operation. Like the first furnace, the second furnace comprises a movable hearth 8 moved by two movable centre bosses 9, l0 and passing with a slow speed through an inlet lock II in a 3 furnace l2 and finally in an outlet lock [3. Said locks have for its object to provide for the heating and cooling of the pieces in a controlled atmosphere.

In Figure 6 both furnaces I and [2 are provided with one and the same hearth I 4 moved by two centre "bosses 15 1'6. Thus,'both"operations of the method are effected successively with the minimum handling.

I claim:

A method of removing oxides, oils and grease from an uncoated metal article which comprises, applying heat to the external surface only of the article in the presence of an oxidizing atmosphere to oxidize oils and grease adhering ,to'the external surface of the article, removing ,tliearticlefrom said heat zone before the articlfis'heatedzsufflciently to alter its internal metallurgical characteristics, applying heat to the external surface only of the article in -a reducing atmosphere to -dcstroy oxides adhering to the external surface of the article, and removing the article from the last heat zone before the article is heated sumciently to alter its internal metallurgical characteristics.

CHRISTIAN ANDRE MAURICE RIPOCHE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,280,825 ,Bacz Oct. 8, 1918 2,116,228 Akin May 3, 1938 2,295,258 Hansen June 18, 1940 2,25 ,980 Turin uly '7, 1942 3,290,552 Gier July 21, 1942 2,367,429 Rauen Jan. 16, 1945 2,388,762 Powers Nov. 13, 1945 Earl Dec. 16, 1947 

